Abstract
Antimicrobial resistance has become a major problem in public health and clinical environments. Against this background, antibiotic susceptibility testing (AST) has become necessary to cure diseases in an appropriate and timely manner as it indicates the necessary concentration of antibiotics. Recently, microfluidic based rapid AST methods using microscopic analysis have been shown to reduce the time needed for the determination of the proper antibiotics. However, owing to the inoculum effect, the accurate measurement of the minimal inhibitory concentration (MIC) is difficult. We tested four standard bacteria: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecalis, against five different antibiotics: piperacillin, cefotaxime, amikacin, levofloxacin, and ampicillin. The results showed that overall, the microfluidic system has a similar inoculum effect compared to the conventional AST method. However, due to the different testing conditions and determination protocols of the growth of the microfluidic based rapid AST, a few results are not identical to the conventional methods using optical density. This result suggests that microfluidic based rapid AST methods require further research on the inoculum effect for practical use in hospitals and can then be used for effective antibiotic prescriptions.
Highlights
We investigate the inoculum effect by image-based Antibiotic susceptibility testing (AST) (IBAST), which is based on a microfluidic biochip
IBAST was performed on S. aureus ATCC 29213 with three β-lactam antibiotics, ampicillin, cefotaxime, and piperacillin, and two non-β-lactam antibiotics, levofloxacin and amikacin
The conventional AST method based on turbidity occurred inoculum effect, so the experiment was conducted in anticipation of this phenomenon in IBAST
Summary
The emergence of antimicrobial resistance is a major issue globally. The pathogens exhibiting this resistance are called “superbugs,” which pose a huge threat in hospitals and in the community [1,2]. The US Centers for Disease Control and Prevention reported that people globally are at risk through the paradigm shift to a “post-antibiotic era” [4]. Antibiotic susceptibility testing (AST) is becoming increasingly important to counter this risk of antibiotic-resistant bacteria, in humans and in animals [5]. AST is a clinical method for detecting bacterial resistance or observing the susceptibility of drugs as opposed to pathogens, enabling determination of the minimal inhibitory concentration (MIC) in each case [6]
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